Asthma Overview and Epidemiology

Asthma

• Asthma is a chronic airway disorder characterized by airway inflammation, hyperresponsiveness, and airflow obstruction.
• Common symptoms include wheezing, shortness of breath, chest tightness, and coughing. Symptoms vary in intensity and time.
• Asthma severity ranges from mild intermittent symptoms to severe, disabling disease.
• Acute asthma exacerbations can be life-threatening.
• International guidelines emphasize treating underlying inflammation to control asthma and reduce risks.

Epidemiology and Etiology

• Asthma is the most common chronic childhood disease and a significant cause of morbidity and mortality in adults and children.
• Worldwide, around 262 million adults and children have asthma.
• In the United States, asthma affects 8% of adults and 7% of children.
• Asthma is the primary diagnosis in millions of physician visits annually and accounts for a large portion of yearly medical costs.
• Asthma is thought to originate early in life and involves complex interactions of genetic and environmental factors (e.g., allergens, occupational sensitizers, infections, tobacco smoke, air pollution, diet, and stress).
• Host factors that increase asthma risk include genes, obesity, sex, and early growth characteristics (e.g., younger gestational age, lower birth weight, greater infant weight gain).

Pathophysiology

• Asthma is characterized by airway narrowing and inflammation in the medium-sized bronchi.
• A key feature is airway hyperresponsiveness (exaggerated narrowing in response to triggers).
• Airway narrowing is a result of smooth muscle contraction, increased mucus, and airway wall edema.
• "Th2 high" inflammation is characterized by early-onset allergic asthma, adult eosinophilic non-allergic asthma, and exercise-induced asthma. Environmental allergens trigger it, often in childhood, and is associated with allergic disease (eczema, rhinitis, food/drug allergies).
• "Th2 low" inflammation is associated with severe, adult-onset asthma, commonly triggered by viral infections, air pollution, and smoking. Obesity is also a factor.

Clinical Presentation and Diagnosis

• Asthma presentation varies from normal pulmonary function (only during acute exacerbations) to significantly reduced function (continuous symptoms).
• Symptoms can arise rapidly (within hours) or gradually over days or weeks.
• Key factors in diagnosis include a detailed medical history, physical exam (upper respiratory and skin), and measurement of expiratory airflow.
• Identifying episodic airflow obstruction, determining reversibility of obstruction, and excluding other diagnoses are critical.
• Tests such as spirometry can assess airway limitation and variability (a bronchodilator test can indicate improvement). Excessive variability in peak expiratory flow or positive exercise/bronchial challenge tests are also indicators.
• Blood tests (e.g., eosinophil count, serum IgE) may provide additional clues.
• Immunoassays can test for allergies (e.g., molds, dust mites, pollen).
• Arterial blood gases and pulse oximetry assess for hypoxemia. FeNO (fraction of exhaled nitric oxide) can reflect airway inflammation.

Treatment

• Goals: maintaining long-term control, minimizing adverse effects, achieving good symptom control, maintaining normal activity, patient satisfaction, preventing exacerbations, preventing loss of lung function.
• Non-pharmacological: Avoiding triggers like allergens, tobacco, pollution and improving emotional well-being.
• Pharmacological: Inhaled corticosteroids (ICS) are the cornerstone of long-term control for all adults and adolescents.
• Other long-term medications include LABAs, LTRAs, and LAMAS.
• Reliever medications: Short-acting beta-2 agonists (SABAs), providing quick relief from acute symptoms. ICS-formoterol and other combinations can be used for both reliever and controller. SAMAs (short acting muscarinic antagonists) may also be used.

Patient Encounter

• Details are provided from patient encounters.
• Typical patient presentations and symptoms are provided to demonstrate presentation patterns of asthma
• Treatment and management are discussed based on patient encounters
• Treatment decisions are based on symptoms, history, testing, and patient preference.
• Asthma action plans can guide self-management.